In domestic appliances, such as for instance dishwashers or washing machines, it may for various reasons be desirable to measure presence of water in the appliance.
As an example, it may be desirable to detect an overfill situation in the appliance. Thus, in order to detect whether a washing compartment of the appliance is filled with an excessive amount of process water, due to e.g. a faulty inlet valve or inferior water filling control, overfill sensors have been used in the art. Typically, the overfill sensors have been embodied in the form of pressure sensors for determining amount of process water in the washing compartment.
In another example, it may be desirable to detect filter clogging in the appliance. Dishwashers comprise a filter at a bottom of a washing compartment for filtering soil from process water being recirculated in the dishwasher by means of a circulation pump. This is undertaken in order to prevent dirty process water from being recirculated and sprayed onto goods to be washed. When an excess amount of soil adheres to the filter, the filter becomes clogged and the water will ultimately not pass through the filter. It may thus be desirable to detect filter clogging such that the filter can be cleaned in order for the dishwasher to reach its full washing capability.
International patent application having publication number WO 2005/089621 discloses a dishwasher and a method of controlling the dishwasher, where effects influencing washing performance negatively such as for example filter clogging are identified by detecting current drawn by a circulation pump of the dishwasher. For instance, if it is detected that the current of the circulation pump fluctuates within a proper range, it is concluded that the filter is clogged and that the pump therefore draws a mixture of air and water. A disadvantage of the approach set forth in WO 2005/089621 is that an absolute level of current drawn by the circulation pump must be detected in order to determine e.g. filter clogging. Such a level may vary with a number of parameters such as age, temperature, type of pump, individual pump variations, etc.